The invention relates to a gear configuration, in particular a superposition gear unit.
Gear configurations in the form of torque division gears or superposition gears are well known in a multiplicity of variations. DE 197 55 612 A1 discloses an apparatus that comprises a gear input shaft, an infinitely variable fixed ratio change-speed gear in form of a traction mechanism gear which is coupled with the gear input shaft and with the gear output shaft; said traction mechanism gear exhibits an input shaft and an output shaft, whereby the input shaft is connected secured against torsion with the gear input shaft, a fixed ratio stage as well as a superposition gear with a first input stage, which is connected secured against torsion with the output shaft of the infinitely variable fixed ratio change-speed gear. Furthermore a second input stage is provided, which can be connected through the fixed ratio stage with the gear input shaft by means of a first clutch and an output stage, which is coupled with the gear output shaft secured against torsion. Thereby the fixed ratio stage is coupled against torsion on the driving side with the gear input shaft and the first clutch arranged regarding the fixed ratio stage on the driven side in such a manner that it alternatively connects the second input stage of the superposition gear on the driven side with the fixed transmission.
With this solution it is possible to make in a simple and easy way a satisfactory multi-use gear available. This solution offers the advantage that at a multi-use gear, created by combining infinitely variable fixed ratio change-speed gear with a superposition gear, so-called Geared Neutral range high meshing speeds within the range of the first clutch are avoided, as this is arranged in a position after a appropriate ratio of the high number of revolutions of the drive shaft on the low number of revolutions (revolution speed) by the fixed ratio stage. This reduces wear and increases the lifetime of the first clutch. A substantial disadvantage exists however in the direct coupling between the infinitely variable change-speed gear, also called CVT, and the gear input and thus the drive shaft. The infinitely variable change-speed gear is thus always coupled to the number of revolutions of the drive engine. A relieving of the superposition gear within a range of higher numbers of revolutions of the drive shaft respectively lower speed ratios of the infinitely variable change-speed gear is thereby achieved in that a second clutch is provided, which connects alternatively the first input stage with the output stage of the superposition gears. Thus a rigid connection between the output shaft of the infinitely variable change-speed gear and the output shaft is created, whereby the superposition gear is spanned in the torque flow. This solution however is characterized by a high number of components and a high requirement for control, as the individual clutches have to be controlled in addition to the CVT. A further substantial problem of the power transfer through the infinitely variable change-speed gear is that due to the appropriate dimensioning only a maximum permissible torque can be transferred, otherwise inadmissible slip conditions can occur with very high loads, which lead to increased wear of the traction mechanism.